6 - Measurements of Energy Expenditure

Question 1

Name the 4 measurements of energy expenditure?

Answer 1

• Indirect Calorimetry
• Lactate Sampling
• VO2 Max Test
• Respiratory Exchange Ratio (RER)

Question 2

Define Indirect Calorimetry?

Answer 2

Measures the production of CO2 and/or the consumption of O2.

• It is a technique that provides an accurate estimate of energy expenditure through gas exchange. It measures how much carbon dioxide is produced and how much oxygen is consumed at both rest and during aerobic exercise.
• Calculating the gas volumes also enables us to find out the main substrate being used (fats or carbohydrates). The accuracy of this test is very reliable and gives you a precise calculation of VO2 (oxygen consumption) and VO2 max.

Question 3

Define Lactate Sampling?

Answer 3

• Blood lactate measurements are used in sports such as swimming, running and rowing to monitor training and predict performance.
• Lactate sampling involves taking a tiny blood sample and a handheld device analyses the blood and indicates how much lactate is present.
• This is an accurate and objective measure of the level of lactate in the blood.
• It can also be used as a means of measuring exercise intensity.
• Lactate sampling can give an idea of level of fitness.

Question 4

Define the VO2 Max Test?

Answer 4

• Tests that can evaluate your VO2 Max include the bleep test, Harvard Step Test and the 12 Minute Cooper Run.
• All these tests give an indication or prediction of your VO2 max. A sports science laboratory can produce much more valid and reliable results using direct gas exchange (which measures the concentration of oxygen that is inspired and the concentration of co2 that is expired).
• Tests using this method involve increasing intensities on a treadmill, cycle ergometer (a stationary bike which measures how much work is being performed) or a rowing machine.
• When a performer is performing a test, they work to exhaustion while the air that is expired is calculated by a computer software. The volume and concentration of oxygen in the expired air is then measured and compared with the % of oxygen that is in the atmospheric air to see how much oxygen has been used during the task.

Question 5

How do you calculate the Respiratory Exchange Ratio (RER)?

Answer 5

RER = Carbon dioxide expired per min (VCO2) / Oxygen consumed per min (VO2

• A RER value close to 1 = performer using carbohydrates
• A RER value of approx 0.7 = performer using fats
• A RER value greater than 1 = anaerobic respiration so more CO2 being produced than O2 consumed.

Question 6

Define Respiratory Exchange Ratio (RER)?

Answer 6

The respiratory exchange ratio is the ratio of carbon dioxide produced compared to oxygen consumed and is used to measure exercise intensity.

• It provides information about fuel usage during exercise. Energy sources such as carbohydrates, fat and protein can all be oxidised to produce energy.
• Calculate in the respiratory exchange ratio will determine which of these energy sources is being oxidised and hence whether the performer is working aerobically or anaerobically.